I tend to leave my car for a month unused while traveling 2-3 times a year and am worried about killing the 12v battery. I've seen mention about people using solar chargers (smart chargers so it doesn't over charge) and was wondering if anyone has any brand recommendations or success stories? Should I hook it up to the trunk battery, or the front hood terminals? Other that potential hydrogen gas buildup when doing the initial hookup in the back, any reason not to wire it up there? Am I correct that the HV battery charges the 12v ONLY when the car is started and running? So I don't have to worry about killing the HV batteries if it sits? Any downsides to this? Thanks!